Background: We have investigated sex ratio at birth (expressed as the proportion of males) in Croatia before, during and after the war (1991-1995).
Methods: Data for each of 21 counties in Croatia (861 516 births) were collected and pooled into two groups: the first, consisting of the counties unaffected by the war, and the second, comprising the counties affected by war events. Odds ratios of being born as a male were calculated, with being born in a county exposed to war defined as the risk factor.
Results: No significant deviations from the expected ratio of 0.514 were found in pre-war, wartime or post-war period at the national level. The ratio was 0.515 during the pre-war and wartime periods, and 0.514 in the post-war period. Comparison of the ratios in the three periods in both affected and unaffected counties revealed no significant increase in the sex ratio. The only significant increase in the sex ratio was registered in two counties unaffected by the warfare.
Conclusions: This study indicates that warfare did not cause a detectable increase of the sex ratio at birth in Croatia, in contrast to what might have been predicted based on earlier reports in the literature.